The respiratory climacteric can be elicited in a variety of fruits as can a pronounced respiratory rise in numerous fleshy storage organs by ethylene, cyanide and low levels of carbon monoxide. The effectiveness of cyanide in this respect has led us to the view that the climacteric-related respiration is mediated by the cyanide-resistant, or alternate path. We will investigate the role of the alternate path in the respiratory climacteric and in ripening by inhibiting the alternate path in thick banana slices which have been exposed to cyanide or CO as ripening initiators. The alternate path is readily inhibited by salicylhydroxamate (SHAM). Antioxidants will also be tested as suppressors of ripening on the presumption that the normally autocatalytic endogenous production of ethylene during ripening represents a free-radical mediated reaction. In this connection we plan to continue investigations of superoxide production by alternate path electron transport, preliminary experiments having indicated that such takes place. Further mitochondrial studies will be undertaken to clarify the relationship between mitochondrial lipid composition and the integrity of the alternate path. Isolated mitochondria from cyanide resistant tissue (e.g. potato tuber) are cyanide sensitive. There is a considerable degradation of phospho- and galactolipid on slicing or homogenizing potato tubers. CN resistance is restored only following a period of phospholipid synthesis. In consequence a relationship is indicated between mitochondrial integrity - especially in regard to membrane lipid composition - and the operation of the cyanide resistant electron transport path. BIBLIOGRAPHIC REFERENCES: Solomos, T. and Laties, G.G. (1976) Induction by ethylene of cyanide-resistant respiration. Biochem. Biophys. Res. Comm. 70: 663-671. Solomos, T. and Laties, G.G. (1976) Effects of cyanide and ethylene on the respiration of cyanide sensitive and cyanide resistant plant tissues. Plant Physiol. In press.